Micrometer-gage



Lb e e h S s t nu e h S 2 .R SMM m@ DW. AE HM G im RR Imm M A d o M o m No. 404,305. Patented May z8, 1889.

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2 Sheets-Sheet 2. 1

(No Model.)

J. RICHARDS.

MIGROMBTBR GAGE.

No. 404,305. Patented May 28, 1889.

Mmmm c/ z i L l UNITED STATES dPATENT OFFICE.

JOHN RICHARDS, OF SAN FRANCISCO, CALIFORNIA.

lvllcRoMETER-GAGE.

SPECIFICATION forming part of Letters Patent No. 404,305, dated May 28, 1889.

Application tiled December 29, 1880l Serial No. 23,067. (No model.)

To all whom it may concern.-

Be it known that I, JOHN RICHARDS, a citizen of the United States, residing at Sanv Francisco, in the county of San Francisco and State of California, have invented certain new and useful Improvements in lVIeasuring-Machilies; andI do hereby declare the following to be a full, clear, and exact description of the invention, such as Will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the letters or iigures of reference marked thereon, which form a part of this specification.

This invention relates to improvements in machines for exact measuring, sometimes called micrometer-gages, the object being to improve a less perfect machine for which Letters Patent No. 219,307 were granted to me on the 2d day of September, 187 9, and which will be hereinafter referred to in this specilication.

The improvements consist, essentially, in the employment of an auxiliary scale in connection with other mechanism to compensate for any error of pitch in the m easuring-screw; also, in placing the measuring-screw above the sliding ways and below the con tact-points carried by the sliding heads; also, in the employment of a divided nut for the measuringscrew clamped transversely to the axis of the screw and attached to one of the sliding heads, and in a split thrust-bearing clamped in the same manner, both being split parallel to the screw and adjustable upon it; also, in a frictional driving-bar operating in connection with a scaled division-Wheel and correcting scale; and, further, in a movable double pointer mounted between the two scales to indicate their relative positions and the time of their coincidence. These various improvements I will now more fully describe, referring for that purpose to the accompanying drawings, in which- Figure 1 is a side elevation of the machine, partly in section. Fig. 2 is a plan view showing the relative position of the several parts of the machine to each other. Fig. 3 is a vertical section on the line cc of Fig. 1. Fig. 4 is an end View and section of the machine with the division-wheel removed. Fig. 5 is an end View of the sliding head to which the measuring-screw is attached, showing the divided nut, by means of which such attachment is made. Fig. 6 is a detail View of the divisionwheel, showing the spring friction-clamp by which the wheel is rotated. Fig. 7 is a detail view, partly in section, showing the screwshaft and thrust-bearing formed thereon.

In the several figures, A represents the frame of the machine, preferably cast in'one piece, an d then iinished by planing and other means until it is of a proper shape to receive the movable parts. A vices, among which are the two movable or sliding heads B B, on which the contactpoints a are mounted, being held in place by screws a. These heads are fitted to slide on the inclined angular ways or surfaces c of the frame, as shown in Fig. 3, the sliding head B being held in any desired position upon the ways by the bolt b, the head of which enters a longitudinal Tshaped groove formed in the frame between the ways, said bolt being provided with the screw-nut d, by which it is tightened on the head. It will be observed that this head B is stationary when the machine is in use, and may be located near or at the desired point on the ways by means of a test-bar, D, placed between the oontactfpoints a when lsetting the head. The sliding head B is of dii-ferent construction, it being the one to which the measuring-screw C is attached, and instead of the positive fixture of the head B it is held down upon the Ways by a bolt, b', of peculiar construction, it being provided with an orifice above the T-head, through which the end of the measuring-screw may pass, and instead of a fixed bearing its nut d rests upon a spring, c', inclosed in the case c, thus holding the head down upon the ways by an elastic or yielding pressure.

It is at best difficult to construct such machines with sufficient accuracy, and as hitherto made the sliding parts have been guided by parallel ways or bars having fiat surfaces, thus involving the necessity of rendering perfect two surfaces at right angles to each other on each Way, and also the parallelism of the ways with each other. In this improved machine the heads B and B', resting on the inclined surfaces of the ways c, depend upon These consist of various de- IOO the truth of said inclined surfaces only to insure accuracy in the movements of the sliding heads, and consequently of the position of the contact-points carried by them.

The measuring-screw C has heretofore been placed beneath the guiding-ways; but in this machine I place this screw above the guidingways and below the contact-points a. This secures a better and more equable movement of the sliding head B', and does not produce so much of a tilting strain when pressing upon a test-bar or other article placed between the contact-points.

The thrust-bearing of my former machine consisted of plain collars, their faces at right angles to the axial line of the screw; but the wear of such faces renders the action of the screw imperfect. I have therefore adopted the series of collars e, which are formed by turning V- shaped grooves in the screwshaft, said grooves being provided with angular faces inclined to the axis of the screw, as shown in Figs. 1 and 7 of the drawings. These collars maybe made with their faces inclined at various angles, and any number desired may be used, and all are equally acted upon by the corresponding inclined grooves of the split bearing D', which is provided with an adjusting-screw, c', by means of which it may be opened or closed upon the collars of the screw t0 insure a perfect fit and avoid `all lost motion. This bearing D is secured to the frame A by three screws, as shown in Fig. 4f, the hole in the bearing through which the screw f passes being slightly elongated or of oval sha-pe, so that by turning the screw c the two parts of the bearing may be made to approach or recede from each other, thus allowing the degree of pressure upon the collars e to be regulated at pleasure; and, as both halves of the bearing D are secured to the frame, they mutually assist each other in resisting the thrusts of the screw.

The nut E, forming the connection between the measurin0-screw and sliding head B', made in two halves held together by screws g, as shown, and the two parts thus connected clamped with a plain face against the sliding head B by screws 7L in such a way as to admit a small degree of lateral adjustment and thus secure a more perfect alignment of the parts, which is always a matter of great difliculty in constructing machines of this class. This nut E, as well as the thrust-bearing, is held in place by screws parallel to the strain and clamped at right angles to the axis of the measuring-screw. This may not seem a matter of importance, but in the construction of such machines the least springing or yielding in the joints becomes apparent in the read ings from the scales; but in this case, both nut and bearing being held in place upon their respective parts of the machine by strong screws, any yielding is prevented that would result in incorrect readings, such as frequently occurred upon machines constructed in the manner described in my former patent from the fastenings then in use.

An important improvement in the construction of this machine is in providing an auxiliary or correcting scale, F, to indicate any error in the pitch or thread of the measuringscrew C. The movable pointer G, journaled upon the screw-shaft, and the division-wheel ll, secured upon a conical bearing near the end of the measurinfj'screw, remain substantially the same in form, except that the pointer has two fingers or points, as shown in Figs. l and 2, one to indicate divisions on the periphery of the wheel II and the other those on the correcting-scale F.

It has been discovered in practice that screws, no matter how carefully they are made, are never perfect in their thread or pitch, and that truemeasurements cannot be made in reading the division-wheel from a single fixed point. The scale F is intended to remedy this defect, the divisions on it representing the errors of the screw, which have been ascertained by comparison with a true standard. The iigures l, 2, 3, and 4t on the scale F are presumed to be the points at which the movable pointer G is set in measuring distances between the centact-points of one, two, three, and four inches, respectively. The corresponding iigures on the division-wheel II being brought opposite, allowance is thus made for any errors of the screw and at vari ous points in its length, as such errors may vary in its different parts. The scales are of course provided with such intermediate di visions as may be required to indicate halves, quarters, &c. These scales are found to vary in an irregular manner when the measuring screws have been made at the same time and by uniform processes.

The scale F is marked on a stationary part of the machine, and requires no adjustment, the necessary adjustment being provided for by turning the divisionwheel II, upon its conical bearing on the outer end of the measuring-screw.

I am aware that scales for indicating the aggregate errors or regular variation of screws have been used, but not in combination with division-scales and a movable pointer showing the relative positions of the two scales.

In comparing two pieces, or in any case where uniform pressure between the contactpoints a is required, the sense of feeling is not nice enough if the screw C and wheel ll are turned positively by a handle attached directl y to the wheel, rendering it necessary to employ a slipping spring or friction bar, I, to which the handle 7s is secured as a means for communicating motion to the` screw, so that when the points a come into contact and a certain pressure is applied the spring orfriction bar I slides on the smooth surface of the wheel lI without effect.

Iam also aware that this in itself is not a new device, the novelty consisting in the con" IOO IIO

I IS

nection with other parts of the machine, by which a new combined result is obtained.

Having thus described my-invention, I claim as new, and desire to secure by Letters Patent of the United States, the following:

l. As an improvement in measuring-machines, the combination, with a dividingwheel, of an auxiliary scale and a double pointer for the purpose of indicating` the errors of the screw, substantially as shown and described.

2. A movable double pointer placed between the scales of a measuring-machine, and in c0111- bination therewith, for the purpose of indicating the relation between an error-scale and a dividing-scale, substantially as set forth.

3. The combination, in a measuring-machine having inclin ed ways, of the measuring-screw, the movable or sliding' heads provided with contact-points, and an adjustable divided nut clamped to one of the heads transversely to the axis of the screw and above the ways, said screws being placed between the contactpoints and ways for the purpose of equalizing strain, substantially as specified.

4. The combination, in a measuring-machine, of a movable double pointer, a divisionwheel, a slip-barl or friction-driver, an errorscale, and a measuring-screw, all constructed and arranged substantially as set forth.

5. The combination, in a measuring-machine, of ways with inclined surfaces, movable heads provided with contact-points, a measuring-screw attached to one of said heads, which is held in place by devices giving an elastic or yielding pressure, a division-wheel having` a slip-bar or frictiondriver, an error-scale,and a double pointer, all constructed and arranged substantially as and for the purpose shown and described.

6. In a measuring-machine, the combination, with the division-wheel, of the measuring-screw and the auxiliary scale adapted to compensate for any error of pitch in said screw, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

JOI-IN RIC HARDS.

Witnesses:

IRA P. RANKIN, A. S. BRAYTON. 

